Categorical calculator

Fisher's exact test calculator

Calculate exact hyper-geometric p-values and odds ratios for 2x2 contingency tables using Fisher's exact test.

Run this test live in StatLab npm i @statlab/core

When to use it

Use for 2x2 tables when sample sizes are small or expected cell counts are < 5.

Required Inputs

  • 2x2 Contingency Matrix counts [[a, b], [c, d]]
  • Alternative hypothesis (two-sided, greater, less)

Mathematical Formula

p = [ (a+b)! (c+d)! (a+c)! (b+d)! ] / [ a! b! c! d! n! ]

Reporting Cautions

  • Valid for 2x2 tables; computationally intensive for larger tables.
  • Provides exact p-values without relying on asymptotic normal approximations.

Code Snippets (Python, R, TypeScript)

Python (SciPy / Statsmodels) 
from scipy import stats
oddsratio, pvalue = stats.fisher_exact([[4, 1], [0, 5]])
print(f"OR={oddsratio:.4f}, p={pvalue:.4f}")
R Language 
fisher.test(matrix(c(4, 0, 1, 5), nrow=2))
TypeScript (@statlab/core) 
import { fisherExact } from '@statlab/core';
const res = fisherExact([[4, 1], [0, 5]]);

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